From 2786cc8695ccfdcb971a959abc7048fae1b7d78a Mon Sep 17 00:00:00 2001
From: EmmanuelNiyonshuti <nemmy0257@gmail.com>
Date: Tue, 15 Sep 2026 13:56:29 +0200
Subject: [PATCH 1/2] fix crash in match statement subject expression

---
 mypy/checker.py                     |  6 ++++++
 test-data/unit/check-python310.test | 14 ++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/mypy/checker.py b/mypy/checker.py
index 33ed5387554d..d4ba6c54fb35 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -6124,6 +6124,12 @@ def _get_recursive_sub_patterns_map(
         sub_patterns_map: dict[Expression, Type] = {}
         typ_ = get_proper_type(typ)
         if isinstance(expr, TupleExpr) and isinstance(typ_, TupleType):
+            if any(isinstance(item, StarExpr) for item in expr.items):
+                # For a starred item (e.g. `*bar`), there's no one-to-one correspondence
+                # between expr.items and typ_.items, we are returning early to avoid an
+                # assertion crash. See: https://github.com/python/mypy/issues/21468.
+                return sub_patterns_map
+
             # When matching a tuple expression with a sequence pattern, narrow individual tuple items
             assert len(expr.items) == len(typ_.items)
             for item_expr, item_typ in zip(expr.items, typ_.items):
diff --git a/test-data/unit/check-python310.test b/test-data/unit/check-python310.test
index 01e490d0da50..a378ae07a57d 100644
--- a/test-data/unit/check-python310.test
+++ b/test-data/unit/check-python310.test
@@ -509,6 +509,20 @@ match m, (n, o):
         pass  # E: Statement is unreachable
 [builtins fixtures/tuple.pyi]
 
+[case testMatchUnpackedTupleSubjectExpressionNoCrash]
+# flags: --strict-equality --warn-unreachable
+# See: https://github.com/python/mypy/issues/21468 
+
+foo: int = 1
+bar: tuple[int, int] = 1, 2
+
+match foo, *bar:
+    case x, y, z:
+        reveal_type(x) # N: Revealed type is "builtins.int"
+        reveal_type(y) # N: Revealed type is "builtins.int"
+        reveal_type(z) # N: Revealed type is "builtins.int"
+[builtins fixtures/tuple.pyi]
+
 -- Mapping Pattern --
 
 [case testMatchMappingPatternCaptures]

From d9202e44bffea62bfec16707cf38a6c7d4e91e13 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 15 Sep 2026 12:42:54 +0000
Subject: [PATCH 2/2] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 test-data/unit/check-python310.test | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test-data/unit/check-python310.test b/test-data/unit/check-python310.test
index a378ae07a57d..33b952f48f49 100644
--- a/test-data/unit/check-python310.test
+++ b/test-data/unit/check-python310.test
@@ -511,7 +511,7 @@ match m, (n, o):
 
 [case testMatchUnpackedTupleSubjectExpressionNoCrash]
 # flags: --strict-equality --warn-unreachable
-# See: https://github.com/python/mypy/issues/21468 
+# See: https://github.com/python/mypy/issues/21468
 
 foo: int = 1
 bar: tuple[int, int] = 1, 2